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Silicon carbide (SiC) is a promising material for high-power, high-frequency and high-temperature devices. The understanding of intrinsic defects in SiC - their origin, electronic structure, annealing behavior and influence on the electrical and optical properties of the material - is essential for defect control. Besides the potential application in electronics, the 3C polytype is also interesting for fundamental studies of defects due to its simple crystal structure.
We used Electron Paramagnetic Resonance (EPR) to study defects in n-type 3C-SiC films irradiated by 3-MeV electrons at room temperature with a dose of 2*1018 cm-2. After electron irradiation, two new EPR spectra with an effective spin S = 1, labeled L5 and L6, were observed. The L5 center has C3v symmetry with g = 2.004 and a fine-structure parameter D = 436.5*10-4cm-1. The L5 spectrum was only detected under light illumination and it could not be detected after annealing at ~550 °C. The principal z axis of the D-tensor is parallel to the <111> directions, indicating the location of spins along the Si-C bonds. Due to relatively weak signals in thin films, no clear hyperfine structure could be detected. However, judging from the symmetry and the fact that the signal was detected under illumination in n-type material, the L5 center may be related to the divacancy in the neutral charge state. Its D-value is indeed similar to that of the P6'b center in 4H-SiC (D = 436*10-4cm-1), which has been identified as one of the two C3v configurations of the neutral divacancy.
The L6 center has a C2v-symmetry with an isotropic g-value of g = 2.003 and the principal x-, y- and z-values of the fine-structure D-tensor: 103.3*10-4cm-1, 215.1*10-4cm-1 and -365.1*10-4cm-1, respectively. The L6 center disappeared after annealing at a rather low temperature (~200 °C), which is substantially lower than the known annealing temperatures for vacancy-related defects in 3C-SiC. This highly mobile defect may be related to carbon interstitials.
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